I've always been a morning person, and an early bedtime works well for me. On weekdays, I need to be up by 5AM to get my daughter on her 6:20AM bus. I'm more than ready to hit the sack by 9PM.
Yes. It is.
I think so. But I think it is more of a routine thing that makes it healthy. For example people who work graveyard shift. Their body's use to being awake during the night hours and sleeping during day light hours. As long as it's their routine, I think it's okay.